Ahahahahahaha. Very true. But I still find it odd that Slipknot, being the main headlining band, is playing shorter than Slayer. Someone on the Mayhem Fest boards said that Slipknot is actually playing for an hour and ten minutes. I don't know if this is true or not.

just throwing out the confirmed signings(as in the bands themselves said so):
Anthrax
Slipknot
Upon A Burning Body

And Phil in a interview said Whitechapel will be doing a signing everyday with all of Whitechapel and I, The Breather confirmed they will be at their merch tent signing after their performance every date on mayhem.

UPDATED: The confirmed signings(as in the bands themselves said so):
Anthrax
Slipknot
Upon A Burning Body
Whitechapel
I,The Breather